function Circle(r) {
    
    this.r = r;

    this.getArea = function() {
        return Math.PI * r * r;
    }

    this.getPer = function() {
        return Math.PI * 2 * r;
    }
}

let circle = new Circle(8);
console.log(circle.getArea());
console.log(circle.getPer());

circle = new Circle(4);
console.log(circle.getArea());
console.log(circle.getPer());